Comma comes before the full subject
Solution 1:
It may do, but that is incidental. In each of your examples, the comma is used to set off a weak interruption to the sentence. Commas are frequently used for this purpose in pairs as bracketing commas, but as Larry Trask points out in his ‘Guide to Punctuation’, ‘Sometimes a weak interruption comes at the beginning or at the end of its sentence. In such a case, one of the two bracketing commas would logically fall at the beginning or the end of the sentence — but we never write a comma at the beginning or at the end of a sentence.’